Fermion pairing with spin-density imbalance in an optical lattice

TL;DR

This paper investigates FFLO-type superfluid states in a polarized two-component Fermi gas within a 3D optical lattice, highlighting their stability, observable signatures, and dependence on system parameters.

Contribution

It demonstrates the stability and observable features of FFLO states in a polarized Fermi gas in an optical lattice, considering effects of filling and interaction strength.

Findings

FFLO states minimize free energy in polarized Fermi gases.

Observable momentum distribution signatures of FFLO states.

Dependence of order parameter on filling and interaction strength.

Abstract

We consider pairing in a two-component atomic Fermi gas, in a three-dimensional optical lattice, when the components have unequal densities, i.e. the gas is polarized. We show that a superfluid where the translational symmetry is broken by a finite Cooper pair momentum, namely an FFLO-type state, minimizes the Helmholtz free energy of the system. We demonstrate that such a state is clearly visible in the observable momentum distribution of the atoms, and analyze the dependence of the order parameter and the momentum distribution on the filling fraction and the interaction strength.